EAS and RFID systems are typically utilized to protect and/or track assets. In an EAS system, an interrogation zone may be established at the perimeter, e.g. at an exit area, of a protected area such as a retail store. The interrogation zone is established by an antenna or antennas positioned adjacent to the interrogation zone.
EAS markers are attached to each asset to be protected. When an article is properly purchased or otherwise authorized for removal from the protected area, the EAS marker is either removed or deactivated. If the marker is not removed or deactivated and moved into the interrogation zone, the electromagnetic field established by the antenna(s) causes a response from the EAS marker. An antenna acting as a receiver detects the EAS marker's response indicating an active marker is in the interrogation zone. An associated controller provides an indication of this condition, e.g., an audio alarm, such that appropriate action can be taken to prevent unauthorized removal of the item to which the marker is affixed from the protected area.
An RFID system utilizes an RFID marker to track articles for various purposes such as inventory. The RFID marker stores data associated with the article. An RFID reader may scan for RFID markers by transmitting an interrogation signal at a known frequency. RFID markers may respond to the interrogation signal with a response signal containing, for example, data associated with the article or an RFID marker ID. The RFID reader detects the response signal and decodes the data or the RFID tag ID. The RFID reader may be a handheld reader, or a fixed reader by which items carrying an RFID marker pass. A fixed reader may be configured as an antenna located in a pedestal similar to an EAS system.
Historically, transmitting, receiving, or transceiver antennas in EAS and RFID systems have been configured as loop-type antennas. A drawback with such loop antennas is that they may be easily de-tuned when installed directly on metal structures, e.g., metal structures in the checkstands of a supermarket, drug store, hypermarket, etc. In addition, the sensitivity of such loop antennas may be adequate in free space. However, the sensitivity of such loop antennas when installed directly on metal structures may also be degraded compared to their sensitivity in free space.
Magnetic core antenna configurations have also been explored for use in such EAS and RFID systems. The core may be formed of a pressed powdered iron or any other suitable magnetic material such as ferrite, an amorphous laminated core, or a nanocrystalline laminated core, etc. A ferrite core antenna may have a high sensitivity and a high quality factor (Q) in free space, which may also make it susceptible to de-tuning and a reduction in sensitivity when placed directly on metal surfaces. One solution to this problem is to space the core antenna off the mounting surface by a mounting distance, e.g., four to five centimeters. However, this spacing solution requires a protrusion of the antenna into an environment where there is a premium on such space. For example, the antenna may protrude into a narrow checkout aisle passageway interfering with customers.
Accordingly, there is a need for a core antenna for EAS and RFID applications to be relatively insensitive to de-tuning when mounted on or near metallic structures, e.g., a checkstand. In addition, there is a need for such an antenna to also maintain relatively high output sensitivity for detection and to not protrude appreciably away from the mounting surface.
Although the following Detailed Description will proceed with reference being made to illustrative embodiments, many alternatives, modifications, and variations thereof will be apparent to those skilled in the art. Accordingly, it is intended that the claimed subject matter be viewed broadly.